JP2756155B2 - Spindle of machine tool - Google Patents

Description

Description: BACKGROUND OF THE INVENTION (Industrial application field) The present invention relates to a main shaft of a machine tool, and in particular, eliminates a metal material as a material to be used as much as possible. The present invention relates to a main shaft of a machine tool that uses a material that was previously used, and has achieved a reduction in weight and a reduction in linear expansion that cannot be achieved with metal material alone.

(Prior Art) Conventionally, heavy steel or alloy steel is used as a spindle material in a conventional machine tool such as a machining center, a boring machine, and a milling machine. This is because steel or alloy steel has a high modulus of elasticity and can have a hard surface, which is suitable in terms of economy including processing.

Meanwhile, the linear expansion coefficient of the steel is in the range of 11~16 × 10 ^-6 ℃ ^-1, for example, the major axis of 2m length there is a temperature change of 10 ° C., the dimensional change of 2.2 to 3.2 × 10 ^-1 mm Will occur.
This means that, for example, when trying to cut a plane with a boring machine, if the temperature of the spindle increases by 10 ° C between the start and end of the cut, a difference in the cut depth of about 0.3 mm will occur. This is a serious problem in producing a highly accurate workpiece. In addition, steel has a high specific gravity, so the weight of the main shaft also inevitably increases, the deformation due to centrifugal force during high-speed rotation is large, the dimensions of the workpiece become unstable, and the vibration damping is small, so it is not suitable for high-speed rotation. Appropriate. If the weight of the main shaft is large, a rise time to high-speed rotation is required, and furthermore, it is necessary to secure power for that.

On the other hand, as a material having light weight and excellent rigidity, for example, a fiber-reinforced composite material such as a carbon fiber-reinforced plastic material (CFRP) is well known, and is used in many fields.
However, the field in which this kind of material is used is limited, and in general, it is mainly used for civil members and aircraft-related members, and is rarely used as a structural material for machines.

In particular, the main shaft of the machine tool is the portion that is most heavily loaded from all directions when machining hard or brittle materials such as metal materials and other ceramics by cutting or grinding, and because it has a cantilever structure, As a material that can withstand this, as described above, a steel or alloy steel that is heavy but has high elasticity and excellent rigidity, and whose surface is easily hardened is used as a matter of course. At present, it is said that practical use of a material having low hardness and abrasion resistance, such as a fiber-reinforced plastic material known to have high properties, is difficult.
As a rare proposal, Japanese Utility Model Application Laid-Open No.
There is a technique disclosed in JP-A-63-96311.

According to the disclosure of Japanese Utility Model Publication No. 60-165101, the ends of a machine-side mounting member and a tool mounting member of a main shaft made of a required shape and material are press-fitted into both ends of a cylinder formed of fiber reinforced plastic. At the same time, the press-fit ends of these members are fixed to the cylinder with an adhesive.

On the other hand, according to the disclosure of JP-A-63-96311,
Although it is different from fiber reinforced plastic, at least a portion of the surface of a cylindrical body made of a C / C composite, which is a similar material, is in contact with at least another member, and has an elastic coefficient and a linear expansion coefficient that are almost equal to the part, such as WC-Co cermet. A high hardness surface forming material is coated by various thermal spraying via an intermediate material for increasing the composite strength of, for example, a metal material such as Mo, W, and Nb, and the coating layer is polished to a predetermined thickness. Has gained shape.

These spindles were developed in search of characteristics not found in conventional metal rollers, and can withstand operation under severe conditions such as machine tools, and are made of ultra-light and rigid materials. It can be said that this technology is noteworthy in that it utilizes high characteristics.

(Problems to be Solved by the Invention) However, the technique disclosed in Japanese Utility Model Application Laid-Open No. 165101/1985 simply press-fits another metal member into a fiber-reinforced plastic cylinder and bonds it with an adhesive. However, since there is a difference in the coefficient of linear expansion between the metal material and the fiber-reinforced plastic material, if the difference is large, peeling is likely to occur on the bonding surface, especially in a portion where the bonding length in the longitudinal direction of the main shaft is long. It is easy. Therefore, in such a portion, a material having a small coefficient of linear expansion must be selected as a metal or ceramic to be applied, and both materials, compositions, and structures are greatly restricted.

On the other hand, the C / C composite (carbon / carbon composite) itself disclosed in JP-A-63-96311 has been used for a long time as a mechanical component, a reactor material, a material for space development, etc. Textiles ”S55.11.1, co-authored by Otani and Kimura, Modern Editors), and the present inventors tried to apply the same material to the main shaft of a machine tool in the same manner as the above-mentioned proposed technology. Due to the difficulties, the development turned to the use of fiber reinforced plastic materials.

That is, the C / C composite is obtained by thermally decomposing the fiber-reinforced plastic composite material at a high temperature and carbonizing the plastic material as a matrix, and as it is, inferior in physical properties. A member is obtained. Therefore, its production requires an extremely multi-step processing step, which inevitably leads to an increase in cost and is expensive.

Therefore, there are the following problems to be solved by the present invention.

(1) Poor dimensional stability caused by the high linear expansion that the conventional steel main shaft necessarily has. It is possible to use a metal material other than steel to make this coefficient of linear expansion smaller than that of steel, but even the smallest Invar alloy that has been published has a coefficient of linear expansion of 1-3 × 10 ^-6 ℃ ^{- 1} and
Furthermore, since this invar alloy is a difficult-to-cut material, and is expensive and has low hardness, it is inappropriate to use it as a main material of the main shaft.

(2) Since the conventional steel main shaft has a large weight, there are various problems derived therefrom. That is, since the deformation due to the centrifugal force during high-speed rotation is large and the vibration damping property is poor,
Since the influence on the processing quality and processing accuracy is large and the moment of inertia is large, it is difficult to further increase the speed, and the required power is also large. To lower the processing accuracy.

(3) For example, in order to obtain a main shaft of a C / C composite, it is necessary to go through a number of steps.

Accordingly, an object of the present invention is to reduce the linear expansion of the main shaft and at the same time to reduce the weight while considering the ease of manufacture and economy.

(Means and Actions for Solving the Problems) In order to achieve the above object, the present invention provides means for solving the above problems described in the claims.

This will be described in more detail below together with the operation.

First, as mentioned above, the present inventors have focused on fiber-reinforced composite materials that have been difficult to put into practical use in the past in the field of machine tools, particularly carbon fiber-reinforced plastic materials (CFRP). I began to consider sex. As described above, CFRP has desirable characteristics as a material for the main shaft in that the coefficient of thermal expansion can be reduced and the weight can be reduced.

However, when looking at the main shaft of the boring machine, for example, chips and the like are easily entangled on the end surface of the main shaft, and are easily damaged if the surface hardness is not high. Because it is dominated by hardness,
Generally, it has a low hardness and suffers from the damage.

Therefore, in order to put CFRP into practical use as a spindle material for machine tools, it must not only compensate for the shortcomings of the conventional spindles using the above steel materials, but also satisfy all the requirements required for machine tool spindles. Must.

In addition, thermal expansion, which is a drawback of a spindle made of conventional steel, is
Regarding the hollow cylindrical structure of CFRP, if the winding angle is properly selected, the coefficient of linear expansion in the longitudinal direction can be reduced to zero or zero, and the absolute value can be suppressed to 0.5 × 10 ^-6 ℃ ^-1 even if it is large. It turned out to be possible. Here, carbon fibers are preferable as the fibers of the fiber-reinforced composite material, and aramid fibers are also conceivable.

Although the hollow cylindrical structure made of CFRP varies depending on the type of fiber or resin, the coefficient of linear expansion shown in Table 1 is generally obtained depending on the winding angle of the fiber.

As shown in Table 1, CFRP has a negative linear expansion coefficient where the winding angle of the fiber is small, and has a larger positive linear expansion coefficient as the winding angle of the fiber increases. Therefore, it is theoretically possible to make the linear expansion coefficient of the hollow cylindrical structure zero or minus by combining these angles or using a specific angle.

The hollow cylindrical structure, which is the main component of the main shaft of the present invention, has the absolute value of the linear expansion coefficient reduced to 0.5 × 10 ⁻⁶ ° C.- ¹ or less by selecting the winding angle of the carbon fiber.
In this hollow cylindrical structure, for example, even if there is a temperature change of 10 ° C. on a main shaft having a length of 2 m, only a dimensional change of 1 × 10 ⁻² mm occurs. When such a hollow cylindrical structure made of CFRP is combined with a metal such as steel, the coefficient of linear expansion can be suppressed to 5 × 10 ^-6 ° C ^-1 or less. Extremely high-precision cutting is possible compared to 16 × 10 ^-6 ° C ^-1 .

Most of the main shaft of the present invention should be substantially CFRP, and a metal material or ceramic is used for a part thereof. Further, fibers other than carbon fibers, for example, glass fibers and aramid fibers can be partially used.

By the way, in most cases, the required performance of the spindle is not only dimensional stability but also bending rigidity and torsional rigidity.
If only one fiber angle is selected so that the coefficient of linear expansion of the hollow cylindrical structure itself becomes zero, the other required performance cannot be achieved. However, by combining at least two types of winding angles of the carbon fibers, the method of setting the linear expansion coefficient to zero can be selected in many cases, so that the degree of freedom in designing other performances is increased. In order to obtain high bending stiffness, the fiber having a winding angle of 0 ° has the highest value, so it is preferable to include this configuration. However, when performing filament wind molding, it is very difficult to wind at 0 °, and ±
(10-15) It is more practical to wrap around. The main spindle itself rotates or the cutting work is performed while the work is rotating, so that torsional rigidity is also required. When the main axis is obtained using CFRP, it is preferable to include ± 45 ° in the laminated structure because the torsional rigidity is maximized when the winding angle of the fibers is arranged at ± 45 °. . Considering disturbance during molding, it is actually ± (40-50) ゜.

Spindle with CFRP-made hollow cylindrical structure according to the present invention is therefore desirable that the wound with an angle of the carbon fiber composed of at least two types, one of which is ± (1 0 to 15) Yes °, while Is more preferably ± (40-50) ゜.
These configurations may be divided into several layers or may be combined. An angle other than these, for example, 90 ° may be added.

By the way, the main shaft of the machine tool is used under extremely severe conditions as described above. In other words, the conditions that must be provided as the main shaft include that the thermal expansion is naturally low, and that the impact resistance is even greater,
The surface hardness is high, and there is no decrease in strength even when the main spindle itself is subjected to mechanical processing.

This will be described with reference to, for example, the main spindle of a horizontal boring machine with reference to FIG. 3. In FIG.
The main shaft 1 receives a large impact and surface pressure due to intermittent cutting such as milling or the like and fluctuation in the thickness of the processed surface. In particular, the impact and the surface pressure are directly received on both side surfaces of the fitting portion A of the tool drive key 2 and the key groove portion B in which the key 3 fixed to the drive gear of the main shaft 1 is fitted.

During boring, the spindle 1 moves in the axial direction inside the sleeve 4 while rotating, and projects from the sleeve 4 for a predetermined length. Get caught in the club. Therefore, if the surface hardness is not higher than the chip, the surface of the main shaft is easily damaged, and the life is shortened accordingly. On the other hand, the holding force of the tool by the draw bar 5 and the collet 6 is as large as 3 tons, and when the tool is mounted, the force is directly received by the tapered surface D of the spindle end. Contact surface E
The above-mentioned force acts on. Therefore, the tapered surface D and the collet contact surface E need to sufficiently withstand high surface pressure. The tapered surface D also receives cutting vibration in addition to the above. Further, the hollow portion of the main shaft 1 accommodates a spring 7 acting when the tool is attached and detached, and the force of the spring is usually 3 to 8 tons. Therefore, the reaction force acts on the end face F of the hollow stepped portion of the main shaft 1 supported by the end face of the helical spring 7, and a large surface pressure is applied similarly to the tapered face D and the collet contact face E.

Also, as shown in FIGS. 1 and 2, the main shaft 1 is not a simple cylindrical member but is formed with, for example, the above-described tapered surface, stepped portion, key groove, screw portion, and the like, and the strength is reduced by such processing. There must be no. For example, when the tool attached to the front end of the main spindle is attached and detached, a reaction force of 3 to 8 tons of a spring acts on the thread G at the rear end of the main spindle, similarly to the end face F of the hollow step. Must be avoided. The adoption of CFRP for boring spindles is no exception, and all of the above conditions must be met.

Therefore, as a result of various investigations, we considered that the main body of the spindle was made of CFRP, and metal, ceramics, etc. were used in the parts where the above conditions were not satisfied with CFRP alone, to supplement the drawbacks of CFRP.

In terms of thermal expansion and rigidity, it has been concluded that even if CFRP is used as described above, it can withstand practical use if the winding angle and the like are appropriately selected. However, it was found at the experimental stage that the above conditions (1) to (4) could not be brought to practical use only with CFRP.

That is, since CFRP has low impact resistance, nitrided steel is used for the fitting portion A and the key groove portion B of the tool drive key, for example.

In particular, the main shaft 1 such as a boring machine needs to be able to move in the axial direction, and must be fixed at an arbitrary position. Therefore, generally, it is made to move in the axial direction by a keyway or a spline or the like, and the outer periphery of the main shaft 1 is fixed by being gripped by the sleeve 4. Therefore,
The outer periphery of the spindle held by the sleeve needs to have a sufficient surface C hardness. Microscopically, the surface of CFRP is a mixture of carbon fiber and resin when viewed microscopically, and it is difficult to simply express hardness. However, in any case, the gripping portion of the main shaft is not suitable for wear. Further, since chips and the like are easily entangled and scratched on the surface of the main shaft 1, high hardness is required to prevent such damage. Therefore, at least the part gripped by the sleeve 4 of the main shaft 1 and the part where the chips are entangled during cutting,
It is necessary to increase the hardness with metals and ceramics. There are various methods for this.
As disclosed in JP-A-162793, the surface of a hollow cylindrical structure made of CFRP can be plated with metal. In particular, hard Cr plating is hard and suitable for this use. Furthermore, hard Cr plating can be applied.

On the surface of the hollow cylindrical structure made of CFRP, the main shaft obtained by sequentially forming a base treatment layer for thermal spraying from the inner layer, a metal sprayed treatment layer, an intermediate plating layer and an outermost plating layer is a hollow cylindrical CFRP cylinder It can be said that the structure and the metal plating layer are firmly bonded to each other, which is a preferable structure.

The aforementioned surface treatment layer for thermally sprayed here, for example, thermal conductivity lambda · S ≧ by ^{0.001cal · cm -1 · sec -1 ·} deg -1 or 0.
Heats non-flat inorganic fillers or inorganic fillers with complex irregularities on the surface, satisfying 05 (λ: thermal conductivity, S: surface area expressed by m ² / g) It is formed by blending with a curable resin, applying to the surface of the carbon fiber composite material, and thermally curing. The material of the metal sprayed layer is not particularly limited as long as it can electroplate the surface of Cu, Ni, Al, F or the like. The material of the intermediate plating layer is selected from the viewpoint of sealing performance and corrosion resistance performance, and as a result of various experiments for such a purpose, it has been found that Cu or Ni is particularly effective. Further, the material of the outermost plating layer is appropriately selected depending on the application, but Ni and Cr are generally employed. In particular, when surface hardness is required, Cr plating is advantageous.

Further, the surface of a hollow cylindrical structure made of CFRP is disclosed in
Ceramic spraying as disclosed in JP-A-534 can also be applied. Alumina-40 titania (Al ₂ O ₃ -40TiO
_{If 2} ) or chromina (Cr ₂ O ₃ ) is used, a robust surface can be obtained.

In this way, the main shaft manufactured by processing the surface of CFRP and using a hollow cylindrical structure that is hardened as the main material has the above-described characteristics required for the gripping portion, and at the same time, is free from scratches caused by cutting chips generated during cutting. It is preferable to be protected and to obtain high dimensional accuracy.

Further, a portion such as a tapered surface D of the spindle end which receives a high surface pressure and cutting vibration is made of nitrided steel or ceramics, and a collet end contact surface E which receives a reaction force of the flat spring 7 is used.
Hard-tempered steel or ceramics is used for the end face F of the hollow step portion and the thread portion G at the rear end of the main shaft.

As described above, the application of metal or ceramics to each part of the main spindle is not limited to metal plating or ceramic spraying on the main spindle surface, and each part is formed of metal or ceramics, fitted into the corresponding part, and bonded with an adhesive. be able to. However, a point to be noted here is that there is a difference in the coefficient of linear expansion between the metal material or ceramic material and CFRP.If the difference is large, peeling is likely to occur on the bonding surface. It is easy to peel off in a long part. Therefore, in such a portion, it is necessary to select a material having a small coefficient of linear expansion for the metal or ceramic to be applied.

Further, in order to prevent separation at the bonding surface and prevent thermal deformation of the entire main shaft, a low thermal expansion metal may be interposed between the metal material or the ceramic material and the CFRP. The presence of the low thermal expansion metal eliminates thermal deformation of the completed spindle as a whole, and at the same time makes it possible to suppress thermal expansion to an extremely low level, thereby enabling ultra-precision machining.

In the above description, the type of carbon fiber may be any of a high-strength type, a medium elastic type, and a high elastic type,
It is needless to say that the use of the highly elastic carbon fiber can provide a main shaft having higher rigidity. Although carbon fibers are mainly described here, some aramid fibers also have a negative linear expansion coefficient in the fiber direction, and the same usage can be performed. There is no particular limitation on the matrix resin. Thermosetting resins, that is, epoxy resin, phenolic resin, polyester resin, vinyl ester resin, polyimide resin can be used, and thermoplastic resin nylon 66, polycarbonate, polyethylene terephthalate, PEEK, PEK, PP
S, PEI, etc. can also be used.

The forming method is not particularly limited, and either a filament wind forming method or a sheet wrap method can be applied.

(Examples) Hereinafter, the present invention will be specifically described by comparing examples and conventional examples.

FIG. 1 is a sectional view of a main shaft of a horizontal boring machine according to a typical embodiment of the present invention.

In the figure, reference numerals 10a and 10b denote inner and outer layers of a CFRP hollow cylindrical structure having different winding angles of carbon fibers forming the main body of the main shaft 1 according to the present invention.

Reference numeral 11 denotes a main shaft end member having a tapered surface into which a shank portion of a tool is inserted. The main shaft end member 11 is made of a steel material alone, and has a small-diameter portion formed on a part of an outer peripheral surface of the inner layer.
It fits and abuts on the step formed on the inner surface of 10a and is bonded and integrated.

12 is an inner layer 10a of the outer diameter of the CFRP hollow cylindrical structure
A hollow cylindrical interposition portion having an inner diameter equal to the inner diameter of the main shaft end member 11 is fitted into the hollow portion of the inner layer 10a such that one end thereof is in contact with the inner end surface of the main shaft end member 11, and is integrally bonded with an adhesive.

Numeral 13 denotes a hollow cylindrical member having a flange at one end made of a steel material. The hollow cylindrical member accommodates a collet and extends to a portion where one end surface of the flat spring comes into contact. The hollow cylindrical member is integrally fitted to the inner surface of the hollow cylindrical interposed member 12 by bonding. Become

A groove 14 having a predetermined length extending parallel to the shaft is formed on the outer peripheral surface of the rear end side of the main shaft of the CFRP hollow cylindrical structure, and a key groove member 15 is fitted and adhered to the groove 14 so that a key is formed. The groove 16 is formed. Further, a hollow cylindrical rear end member 17 having a flange and a key groove 17a is fitted and fixed to the inner surface of the rear end portion of the hollow cylindrical structure made of CFRP with an adhesive. The inner diameter of the hollow cylindrical rear end member 17 is set equal to the inner diameter of the inner layer 10a.

A hard metal or ceramic coating layer 18 is formed on the outer surface of the spindle 1 after the assembly of these members.

Example 1 A hollow cylindrical structure serving as a main body of a spindle was manufactured using CFRP. This hollow cylindrical structure has an outer diameter of 110m.
m, length 1590 mm, medium-elastic carbon fibers such that the inner diameter 64.7mm and (Mitsubishi Rayon Co. PYROFIL ^R MM-1) used was molded by filament winding method. The matrix is an epoxy resin. The inner layer 10a had a winding angle of ± 45 °, and the outer layer 10b had a winding angle of ± 10 °, so that the respective thicknesses were 18.65 mm and 4 mm. After this is sufficiently cured, the necessary portions are subjected to cutting and grinding, and the main shaft end member 11, hollow cylindrical interposition member 12, hollow cylindrical member 13, key groove member 15, and hollow cylinder The rear end members 17 were fitted and fixed by bonding. Thereafter, machining and finishing were again performed, and a conductive coating was applied to the outer surface thereof. Then, Cu plating and Cr plating were sequentially performed by electroplating to form a coating layer 18 and further grinding and finishing.

Here, SACM645 was used for the main shaft end member 11, Invar alloy was used for the hollow cylinder interposition member 12, and SCM440 hard-tempered steel was used for the hollow cylinder member 13, the keyway member 15, and the hollow cylinder rear end member 17. .

Note that the inner layer 10a made of CFRP and the SCM440
The hollow cylindrical member 13 made of an invar alloy, which is a low expansion alloy, is interposed between the hollow cylindrical member 13 made of a high-contrast material.

The spindle 1 according to the present embodiment thus obtained has a total length of 1815 m.
m, weight (W) 32 kg, flexural rigidity (EI) 6.4 × 10 ¹⁰ kgf
・ Mm ² , the torsional rigidity (GIp) is 2.93 × 10 ¹⁰ kgf ・ mm ² ,
Regarding thermal expansion, the dimensional change when the temperature rises by 15 ° C is 9
It was found that they only contracted μ (−9μ).

Table 2 shows a comparison of this with a conventional spindle (made by our company) made only of steel.

(1) If the weight of the main shaft is reduced from 92 kg to 32 kg, there are the following merits.

Improvement of spindle control performance by reduction of moment of inertia,
Easy to speed up.

In the spindle according to the present embodiment, the moment of inertia is reduced to 25% of that of the conventional spindle made of steel, and the torque required to cause the spindle to rise from a stationary state to a high-speed rotation per unit time is also 25% of the steel spindle.

This leads to shortening of the rise time to high-speed rotation, which means that high-speed rotation is facilitated. For example, in tapping, normal and reverse rotation can be repeated at high speed.
Further, for example, the torque required for accelerating to 3000 rpm in the same time is sufficient for the spindle according to the present embodiment at 25% of the conventional value, so that the work amount is small and the heat generation is small. As a result, energy is saved and thermal displacement is reduced.

 Improved spindle positioning accuracy.

In a machine tool having a spindle feed-out mechanism, a reduction in the weight of the spindle results in a reduction in slip resistance during spindle feed-out, thereby reducing the torsion angle of the drive system of the feed-out mechanism and improving positioning accuracy.

(2) According to Table 2, the spindle according to the present embodiment has a lower rigidity value than the conventional example, but the above values for both the bending rigidity and the torsional rigidity can sufficiently be put to practical use.

What is the value of the conventional example above is the value of our product as an example and is intended for low-speed and high-torque cutting, and the torque (75 kg.m) according to this embodiment is applied to a general spindle of the same class for machining centers. In many cases, it can be said that the rigidity is sufficient.

(3) The thermal expansion when the temperature rises by 15 ° C. contracts by 9 μm in the spindle according to the present embodiment, but increases by 250 μ in the spindle according to the conventional example.

This particularly affects the machining accuracy in the depth direction of the hole. Generally, heat is generated around the spindle during machining, and according to the conventional spindle, the temperature of the first hole before the temperature rise is increased by 9 ° C when the temperature rises by 15 ° C. At the individual hole, a difference of as much as 250 μm occurs in the depth. On the other hand, in the spindle according to this embodiment, the error is within 10μ even if viewed simply, and machining can be performed with high precision. However, the elongation due to heat generated during cutting of the tool, for example, a tool length of 300 mm and a tool temperature increase of 5 ° C. Then, when combined with the extension of 15 μ, the total extension of the spindle and the tool becomes 15 (μ) −9 (μ) = 6 (μ), and a more favorable result is obtained.

Example 2 Filament wind molding was performed using the same material so that the hollow cylindrical structure forming the main body of the main shaft had the same shape and size as in Example 1. After hardening this sufficiently, it was subjected to grinding and cutting, and the same type of steel or alloy was adhered to the necessary parts as in Example 1, and then machined again to finish. After masking necessary portions, bond coat coating was performed and then cured, and then Cr ₂ O ₃ was plasma-sprayed thereon and ground so as to meet dimensions.

The thermal expansion and rigidity of this shaft were almost the same as in Example 1.

Example 3 Filament wind molding was performed using the same material so that the hollow cylindrical structure forming the main body of the spindle had the same shape and size as in Example 1. After this was sufficiently hardened, grinding and cutting were performed, and the same type of steel or alloy was adhered to the necessary parts as in Example 1, and then machined again to finish. After masking the necessary part, the outer surface was subjected to thermal spraying undercoating, and after performing copper thermal spraying treatment, Cu plating and hard Cr plating were sequentially performed by electroplating and ground to the dimensions .

The thermal expansion and rigidity of this shaft were almost the same as in Example 1.

(Effects of the Invention) As described above in detail, according to the present invention, the weight reduction as the main shaft of the machine tool is realized, and the thermal expansion in the axial direction can be reduced, so that the processing accuracy is further improved.

Furthermore, the weight reduction and the reduction of the linear expansion lead to energy saving and speeding up.

[Brief description of the drawings]

1 is a longitudinal sectional view showing one embodiment of a main shaft of a machine tool according to the present invention, FIG. 2 is a transverse sectional view taken along line XX of FIG. 1,
FIG. 3 is a partial vertical sectional view of a spindle head portion of a horizontal boring machine. Explanation of main parts in the figure 1 .... Main shaft 10a ... (CFRP) inner layer 10b ... (CFRP) outer layer 11,12,13,15,17,18 ... Metal 16 ... Key groove

Continued on the front page (72) Inventor: Sai Kodama 4-1-1-60 Sunadabashi, Higashi-ku, Nagoya-shi, Aichi Prefecture Inside Mitsubishi Rayon Co., Ltd. (72) Inventor Takeo Gomi 4-1-1, Ushikawa-dori, Toyohashi-shi, Aichi Prefecture Mitsubishi Rayon Co., Ltd. In-company (56) References JP-A-63-96311 (JP, A) JP-A-50-21065 (JP, A) JP-A-60-165101 (JP, U) (58) Fields investigated (Int. . ⁶ , DB name) B23B 19/02

Claims (4)

(57) [Claims] 1. A main body is formed of a hollow cylindrical structure made of a fiber-reinforced composite material, and metal or ceramic is disposed on a part or all of an outer peripheral surface, an inner peripheral surface, or an end portion of the hollow cylindrical structure. The fiber is a carbon fiber or an aramid fiber, and at least one of the winding angles of the fiber is in a range of ± (10 to 15) °, and at least one of the winding angles is ± (40). 2 in the range of ~ 50) ゜
Type, between the hollow cylindrical structure and metal or ceramics,
A main shaft of a machine tool in which a metal material having a lower thermal expansion than the metal or ceramic is interposed. 2. The main shaft according to claim 1, wherein the absolute value of the coefficient of linear expansion in the longitudinal direction of the hollow cylindrical structure is 0.5 × 10 ⁻⁶ ° C.- ¹ or less. 3. The main shaft according to claim 1, wherein said hollow cylindrical structure and said metal or ceramic are fixed with an adhesive. 4. The main shaft according to claim 1, wherein the fixing of the hollow cylindrical structure and the metal or ceramic is performed by metal plating or ceramic spraying.